Heatable laminated windshield construction

ABSTRACT

A heatable, laminated windshield construction is disclosed in which an electrical connection is made to a transparent interlayer which has a conductive coating thereon. When power is supplied to the conductive coating, the result is a heating of the windshield. The connection to the conductive coating is completely sealed so that the moisture is unable to penetrate the laminated construction.

United States Patent [191 Boaz et a1.

[4 1 Feb. 5, 1974 1 HEATABLE LAMINATED WINDSHIELD CONSTRUCTION [75]Inventors: Premakaran T. Boaz, Southgate;

Roman Surowiex, Center Line, both of Mich,

[73] Assignee: Ford Motor Company, Dearborn,

Mich.

[22] Filed: Mar. 26, 1973 [21] Appl. No.: 345,168

[52] US. Cl 219/522, 219/203, 219/541, 219/543 [51] Int. Cl. H05b 3/06[58] Field of Search... 219/203, 522, 541, 543, 544; 161/192; 244/134;296/84 [56] References Cited UNITED STATES PATENTS 2,991,207 7/1961Miller 219/203 3,020,376 2/1962 Hofmann et a1. 219/543 X 3,288,98311/1966 Lear, Sr. 219/522 3,330,942 7/1967 Whitson 219/522 3,356,83312/1967 Orcutt 219/522 3,718,535 2/1973 Armstrong et a1 219/203 XPrimary Examiner-Volodymyr Y. Mayewsky Attorney, Agent, or FirmWilliamE. Johnson; Keith L. Zerschling [57] ABSTRACT A heatable, laminatedwindshield construction is disclosed in which an electrical connectionis made to a transparent interlayer which has a conductive coatingthereon. When power is supplied to the conductive coating, the result isa heating of the windshield. The connection to the conductive coating iscompletely sealed so that the moisture is unable to penetrate thelaminated construction.

4 Claims, 2 Drawing Figures HEATABLE LAMINATED WINDSHIELD CONSTRUCTIONBACKGROUND OF THE INVENTION construction in which an electricallyconductive, laminating interlayer is bonded between a pair oftransparent glass sheets to form the windshield. Electrical power isapplied to the conductive material in order to defrost or defog thewindshield. In order to produce a FIG. 2 is a cross section through theconstruction of FIG. 1 after formation of the windshield in a laminatingoperation.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown anembodiment of a windshield, generally identified by the numeral 10,fonned in accordance with the teachings of this invention. As

0 best seen in this Figure, the windshield is formed from windshieldwhich is acceptable for commercial use, the Y windshield must be sealedabout all of its lateral edges in such a manner that moisture or othercontaminants cannot penetrate into the interlayer. This applicationteaches an electrical connection to the conductive material on theinterlayer in such a form that the area of electrical connection issealed to moisture and other contaminant penetration.

SUMMARY OF THE INVENTION This invention is directed to a laminatedwindshield construction for a vehicle and, more particularly, to animproved heatable, laminated windshield construction wherein anelectrical connection to an electrically conductive, heatable interlayerwithin the interior of the windshield is formed so that it resists thepenetration thereof by moisture and other contaminants.

In accordance with the teachings of this invention, a heatable,laminated windshield for a vehicle has a transparent interlayer having apair of principal faces with a conductive coating on at least one of thefaces. The conductive coating is one which produces heat when anelectrical current is applied thereto. The transparent interlayer alsohas a notched out portion which would be adjacent an area of the edge ofthe final windshield construction. First and second laminatinginterlayers are positioned adjacent both principal faces of thetransparent, heatable interlayer. First and second transparent glasssheets are positioned adjacent the laminating interlayers. A circuitboard, including a non-conductive base with conductive paths thereon, ispositioned so that a portion thereof resides within the notch of thetransparent layer and another portion thereof extends out beyond theperipheral edges of the laminated windshield. Electrical circuit pathsare formed, in part, on the conductive coating of the transparentinterlayer and, in part, on the conductive paths of the circuit board toconnect electrically the conductive paths of the circuit board to theconductive coating. An additional sealing material is provided to fillin the free volume about the notch of the transparent interlayer whenthe windshield is subjected to heat and pressure in a laminatingoperation. In a normal state, the sealing material does not fill thefree volume but is flowable thereinto during the laminating operationwhich bonds all of the elements into a single unit to form the laminatedwindshield construction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded, perspectiveview of various components necessary to form the windshield constructionof this invention. These components are shown in a disassembledcondition in this FIG.

an upper transparent glass sheet 12 and a lower transparent glass sheet14. A first laminating interlayer 16 is adjacent the upper lite and asecond laminating interlayer 18 is adjacent the lower lite. Theseinterlayers may be formed from a material such as polyvinylbutyral.Disposed between the first and the second laminating interlayers is atransparent interlayer 20. This interlayer has upper and lower principalfaces identified respectively by the numerals 22 and 24 in FIG. 1 only.The interlayer will have a conductive coating on the upper surfacethereof of a nature taught in Canadian Pat. No. 844,570. The coating onthe interlayer is of such a nature that it reduces only slightly thetransmission of light through the windshield but yet is of sufficientthickness to carry the current necessary to develop the heat required todefog or to defrost the windshield. The transparent interlayer 20 alsohas a notched out portion 26 which is adjacent leading edges 28 and 30respectively of the upper and lower transparent glass sheets.

A circuit board, generally identified by the numeral 32, is formed of anon-conductive base portion 34 which supports circuit paths 36 and 38.The circuit paths may be formed by bonding thin copper foil to the base.The circuit board may also be formed in any of the many ways known tothose skilled in the art.

An electric circuit path 40 and an electric circuit path 42,respectively connect the circuit paths 36 and 38 to the electricallyconductive coating on the upper face 22 of the transparent interlayer20. These latter mentioned circuit paths are formed of thin copper foiland are bonded to the circuit paths on the circuit board 32 by a weldingoperation. The location and direction of the circuit paths 40 and 42 andtheir manner of connection is illustrated in greater detail in thepreviously mentioned patent application Ser. No. 316,322.

A sealing structure, generally identified by the numeral 44, is in theform of a U-shaped member having a pair of legs 46 and 48 and aninterconnecting member 50. This member may be made out of any materialwhich is relatively stable at room temperature but which is flowablewhen subjected to the heat and the pressure encountered in a routineglass laminating operation. For example, the member may be made out ofthe same polyvinylbutyral that is utilized to form the laminatinginterlayers 16 and 18. The member may be positioned above or below theelectric circuit paths. One leg 46 is designed to fill the area betweenthe base 34 of the circuit board 32 and juxtaposed side wall portion ofthe notched out portion 26 of the transparent interlayer 20. Similarly,the second leg 48 is designed to seal the area between the base and theedge of the notched out portion on the other side of the circuit board.The interconnecting member 50 of the sealing structure 44 is designed tofill the areas and seal the area at the point where the circuit boardcomes in contact with the deepest portion of the notched out portion ofthe transparent interlayer. The sealing is best illustrated in FIG. 2which shows the material 44 filling all of the voids, this fillingtaking place when the material is soft enough to flow during the heatand pressure encountered by it in a glass laminating operation.

it will, of course, be obvious that the sealed connection to aconductive interlayer may be accomplished by employing sealing strips ononly the lateral edges of the circuit board that is resident within thenotched out portion of the interlayer. Also, a liquid plastic materialmay be applied to the areas between the circuit board and the walls ofthe notched out portion of the interlayer and allowed to dry to a solidmaterial, the solid being one, which fully cures during the heat andpressure of the glass laminating operation.

The desirability of sealing this area of electrical connection is quitehigh. If moisture or other contaminants are allowed to penetrate thewindshield they may cause a short circuit condition to exist between theconductive coating on the interlayer and some metal objects supportingthe windshield in a vehicle. if a short circuit condition occurs, theinterlayer will burn out and the entire windshield will have to bescrapped.

Many modifications of this invention will be apparent to those skilledin the art in view of the teachings of this specification. It isintended that all such modifications which fall within the attendedclaims.

We claim:

1. A heatable, laminated windshield construction which comprises:

a transparent interlayer having a pair of principal faces with aconductive coating on at least one of said faces, said conductivecoating being one which produces heat when an electrical current isapplied thereto, said transparent interlayer having a notched outportion,

first and second laminating transparent interlayers positioned adjacentboth principal faces of said transparent interlayer,

first and second transparent glass sheets positioned adjacent and bondedto said laminating interlayers;

a circuit board including a non-conductive base with conductive pathsthereon, said circuit board extending at least in part into said notchof said transparent interlayer;

electrical circuit path means in part on said conductive coating of saidtransparent interlayer and in part on said conductive paths of saidcircuit board for electrically connecting said conductive paths of saidcircuit board to said conductive coating; and

sealing means for filling in the free volume about said notch of saidtransparent interlayer when said windshield is subjected to heat andpressure in a laminating operation.

2. The windshield construction of claim 1 wherein:

said sealing means is formed of the same material as said laminatinginterlayers.

3. The windshield construction of claim 2 wherein:

said sealing means is a U-shaped piece of material in which each of thelegs thereof in part overlays a juxtaposed portion of both a side ofsaid circuit board and a portion of said notched out portion of saidtransparent interlayer, and in which the connecting portion of saidU-shaped piece of material overlies the juxtaposed portion of the frontof said circuit board and said transparent interlayer.

4. The windshield construction of claim 3 wherein:

said electric circuit path means are formed by thin paths of copperfoil.

1. A heatable, laminated windshield construction which comprises: atransparent interlayer having a pair of principal faces with aconductive coating on at least one of said faces, said conductivecoating being one which produces heat when an electrical current isapplied thereto, said transparent interlayer having a notched outportion, first and second laminating transparent interlayers positionedadjacent both principal faces of said transparent interlayer, first andsecond transparent glass sheets positioned adjacent and bonded to saidlaminating interlayers; a circuit board including a non-conductive basewith conductive paths thereon, said circuit board extending at least inpart into said notch of said transparent interlayer; electrical circuitpath means in part on said conductive coating of said transparentinterlayer and in part on said conductive paths of said circuit boardfor electrically connecting said conductive paths of said circuit boardto said conductive coating; and sealing means for filling in the freevolume about said notch of said transparent interlayer when saidwindshield is subjected to heat and pressure in a laminating operation.2. The windshield construction of claim 1 wherein: said sealing means isformed of the same material as said laminating interlayers.
 3. Thewindshield construction of claim 2 wherein: said sealing means is aU-shaped piece of material in which each of the legs thereof in partoverlays a juxtaposed portion of both a side of said circuit board and aportion of said notched out portion of said transparent interlayer, andin which the connecting portion of said U-shaped piece of materialoverlies the juxtaposed portion of the front of said circuit board andsaid transparent interlayer.
 4. The windshield construction of claim 3wherein: said electric circuit path means are formed by thin paths ofcopper foil.